Handling temporary files in BASH shell scripts

Temporary files left over from shell scripts clutter up your /tmp directory and may result in information leakage. Below are a pair of functions we use to gracefully handle the creation and removal of temporary files in shell scripts.

The first function is used to create a temporary file:

function os_mktemp {
 [[ ! $1 ]] && echo “os_mktemp: required a handle name” && exit 99
 let OS_TEMPFILEHANDLE++;
 OS_TEMPFILE[$OS_TEMPFILEHANDLE]=`mktemp /tmp/ostmp.XXXXXXXX`
 eval F_$1=${OS_TEMPFILE[$OS_TEMPFILEHANDLE]}
}


It requires a single parameter, which is used to create a variable name containing the path to the temporary file. For example. os_mktemp FTPOUTPUT will return a variable $F_FTPOUTPUT.

The array OS_TEMPFILE is an array holding the names of all the temporary file names, this is used by the cleanup function to remove the temporary files.

os_mktemp OUTPUT; this results in a temporary file with a random name being created and the name being stored in the variable $F_OUTPUT.

The second function is used to remove all temporary files.


function os_cleanup {
 for FILE in ${OS_TEMPFILE[@]}; do
  [[ -e "$FILE" ]] && rm “$FILE” || echo “os_cleanup: couldn’t remove temporary file $FILE.”
 done
}


To ensure the os_cleanup code is executed whenever the shell script closes, we use the BASH trap command.


trap os_cleanup INT TERM EXIT


Tags: bash, ftp